The present invention is related to devices that generate electric power from the radiation of electronically charged particles. Particles of this type are known as beta particles that are negatively or positively charged. Beta particles, as is well known, have a very small but finite mass and travel at very high velocities and therefore do possess a measure of kinetic energy, which, according to the laws of physics is equal to the mass multiplied to the velocity squared.
Electrons are emitted from various sources and especially from the surface of certain very hot metals such as cesium and from radio-active elements such as radium, plutonium, thorium, uranium and from many isotopes of normally not radioactive elements.
Some examples of particle-emitting sources are Promethium-147 (chemical sign Pm-147) where the Figure 147 designates a heavy isotope with nucleous weight of 147. This material emits negative beta particles with an energy corresponding to 0.23 mega volts. Thallium-204 (Tl-204) is another source of negative beta particles, having an energy corresponding to 0.765 mega volts. A source of positive beta particles is Sodium-22 (Na-22), which emits particles at an energy level of 0.54 mega volts.
The above energy sources spend their energy such that the active material is spent approximately within a time frame of 2 to 3 years, which represents the so-called half-life of the material.
Inventors have in the past sought to construct electronic power generating apparatus based on the radiation of electrically charged particles.
U.S. Pat. No. 3,021,472 by K. G. Hernqvist issued Feb. 13, 1962 describes a thermionic energy converter in which a heated cathode emits electrons that are intercepted by a collecting electrode.
U.S. Pat. No. 3,178,631 by D. H. Sweet, issued Apr. 13,1965 describes electric power generating apparatus containing an internal core of radio-active material surrounded by collectors which collect the electrons emitted from the radio-active material. The electric energy received by the collectors is in nature of a very high voltage and of a very low amperage, and is direct currect (DC). Such energy is difficult to convert to more useable type energy of lower voltage and higher current, due to the fact that it is of direct current (DC) nature, and must therefore first be converted to alternating current (AC) before it can be converted in a transformer to energy of lower voltage and higher current. Referenced patent by D. H. Sweet proposes a method of conversion consisting of beam switching tubes in which reflecting electrodes switch a beam of electrons from a hot cathode back and forth between two collecting electrodes that are in turn connected to a primary winding of a transformer, the secondary winding of which produces alternating current of stepped-down voltage. Referenced patent however, suffers from the drawback that the additional apparatus required for the energy conversion leads to increased complexity and cost as well as energy loss and reduced reliability.
The present invention avoids these problems by means of a beam switching arrangement that is performed directly in the vessel containing the radio-active material and by switching directly the beams of particles emitted by the radio-active material by means of external reflecting electrodes that are interacting with the collecting electrodes, as is described in greater detail in the following description and the appended drawings.
It is therefore a primary object of the present invention to provide apparatus for generating electronic energy from radioactive materials which converts directly the kinetic energy of the charged particles to electric energy by switching the particle beam between the collecting electrodes.
It is a further object of the invention to provide apparatus for collecting a maximum amount of the available particle energy by means of a stepped system of collecting electrodes that are disposed at increasing distances from the particle emitting material.
It is a further object of the invention to provide apparatus that yields a high degree of efficiency by converting the DC-current produced by the particle beam directly into AC-current which can be readily converted to lower voltage in a transformer connected to the collecting electrodes.
It is still another object of the invention to perform the beam-switching operation by means of AC-voltage derived directly from the aforesaid transformer without intervening switching apparatus.
It is still another object of the invention to provide apparatus for generating electric energy from a radio-active particle source that is simple and reliable in construction and that is capable of production without undue complexity.
Other advantages and objects of the invention will become clear in the course of the following description.